6CG6

The 6CG6 is a miniature variable-transconductance pentode, classified by Sylvania as remote-cutoff. Its characteristic allows transconductance to decrease progressively as the control-grid voltage becomes more negative: the sheet gives 2 mA/V at −8 V, falling to 40 µA/V at −24 V under the manufacturer's stated conditions. The available document is Sylvania's registration sheet dated 30 August 1950, citing RMA release No. 914 of 10 October that year. These dates document the sheet and registration without, by themselves, establishing the start of commercial production.

Heating is indirect, with a 6.3 V, 300 mA heater suitable for AC or DC supply. The seven-pin miniature base is B7G: pin 1 connects to the control grid, pin 2 to the suppressor grid and internal shield, pins 3 and 4 to the heater, pin 5 to the anode, pin 6 to the screen grid and pin 7 to the cathode. For the listed characteristics, Sylvania specifies connecting pins 2 and 7 at the socket; external shield No. 316 also connects to these pins. Maximum control-grid-to-anode capacitance is 0.008 pF, while input and output capacitances are both 5 pF. Mounting is permitted in any position.

The tabulated operating point uses an anode voltage of 250 V, a screen-grid voltage of 150 V and a control-grid voltage of −8 V, with the suppressor grid at cathode potential: anode current is 9 mA, screen current 2.3 mA and internal resistance 0.72 MΩ. These are operating characteristics, distinct from the Design Center maximum ratings: 300 V at the anode, 150 V at the screen grid, 4 W anode dissipation and 0.75 W screen dissipation. The control grid must not have a positive DC voltage; the maximum permissible heater-to-cathode voltage is ±90 V. Keeping anode and screen-grid voltages separate is essential when reading this sheet.